This randomized clinical trial will test the primary hypothesis that the recurrence rate of large bowel adenomatous polyps will be lower in persons with a low-fat, high-fiber and high vegetable and fruit dietary pattern than in those with the customary high-fat, low-fiber and low vegetable and fruit U.S. dietary pattern. The primary endpoint to be assessed in this study is whether or not a participant has a recurrence of a large bowel adenomatous polyp and characteristics of all recurring adenomatous polyps.